Particle Identification Detector Research Articles

Absolute momentum calibration of the HARP TPC

In the HARP experiment the large-angle spectrometer is using a cylindrical TPC as main tracking and particle identification detector. The momentum scale of reconstructed tracks in the TPC is the most important systematic error for the majority of kinematic bins used for the HARP measurements of the double-differential production cross-section of charged pions in proton interactions on nuclear targets at large angle. The HARP TPC operated with a number of hardware shortfalls and operational mistakes. Thus it was important to control and characterize its momentum calibration. While it was not possible to enter a direct particle beam into the sensitive volume of the TPC to calibrate the detector, a set of physical processes and detector properties were exploited to achieve a precise calibration of the apparatus. In the following we recall the main issues concerning the momentum measurement in the HARP TPC, and describe the cross-checks made to validate the momentum scale. As a conclusion, this analysis demonstrates that the measurement of momentum is correct within the published precision of 3%.

The first version buffered large analog bandwidth (BLAB1) ASIC for high luminosity collider and extensive radio neutrino detectors

Future detectors for high luminosity particle identification and ultra high energy neutrino observation would benefit from a digitizer capable of recording sensor signals with high analog bandwidth and large record depth, in a cost-effective, compact and low-power way. A first version of the buffered large analog bandwidth (BLAB1) ASIC has been designed based upon the lessons learned from the development of the large analog bandwidth recorder and digitizer with Ordered Readout (LABRADOR) ASIC. While this LABRADOR ASIC has been very successful and forms the basis of a generation of new, large-scale radio neutrino detectors, its limited sampling depth is a major drawback. A prototype has been designed and fabricated with 64 k deep sampling at multi-GSa/s operation. We present test results and directions for future evolution of this sampling technique.

The LHCb RICH photon detector system

The LHCb experiment at the CERN Large Hadron Collider will employ two Ring Imaging Cherenkov (RICH) detectors for particle identification. The Cherenkov photons will be detected by planes of photon detectors covering a total active surface area of 2.1 m 2. The detector chosen for this task is the pixel hybrid photon detector (HPD). This combines silicon pixel sensors, integrated electronics and high-density interconnects together with vacuum-tube technology to produce an efficient, low-noise detector sensitive to single photons. For the complete photon detector system of the LHCb RICH, 484 such HPDs are required and these have been fully integrated into detector modules. Specific aspects of this integration within the RICH system are described together with the steps taken to ensure the efficiency and reliability of the detector in the harsh environment of LHCb.

The High Momentum Particle Identification Detector in ALICE at LHC

The ALICE High Momentum Particle Identification Detector (HMPID) is a proximity focusing ring imaging Cherenkov (RICH) for the hadron discrimination at high transverse momenta ( 1 < p t < 3 GeV/c for π and k, 1 < p t < 5 GeV/c for p). This paper focus on the HMPID particle identification (PID) capabilities in the expected charged particle occupancy dN ch / d η = 6000 , simulated in central Pb-Pb ALICE events.

Experience from the construction and installation of the HMPID CsI-RICH detector in ALICE

The construction and installation phases of the High Momentum Particle IDentification (HMPID) detector of the ALICE experiment were completed by summer 2006. The total active area of the detector is 11 m 2 . It represents the largest scale application of CsI photo-cathodes in RICH detectors to date. We will report on the production of the CsI photo-cathodes, the readout electronics, the Multi-wire Proportional Chambers (MWPCs) and the assembly and handling procedures needed to produce such a large detector.

The current progress of the ALICE Ring Imaging Cherenkov Detector

Recently, the last two modules (out of seven) of the ALICE High Momentum Particle Identification Detector (HMPID) were assembled and tested. The full detector, after a pre-commissioning phase, has been installed in the experimental area, inside the ALICE solenoid, at the end of September 2006. In this paper, we review the status of the ALICE/HMPID project and we present a summary of the series production of the CsI photo-cathodes. We describe the key features of the production procedure which ensures high-quality photo-cathodes as well as the results of the quality assessment performed by means of a specially developed 2D scanner system able to produce a detailed map of the CsI photo-current over the entire photo-cathode surface. Finally, we present our recent R&D efforts toward the development of a novel generation of imaging Cherenkov detectors with the aim to identify, in heavy-ion collisions, hadrons up to 30 GeV/ c.

Future charged kaon decay experiments

Future experiments aiming to perform precise measurement of rare kaon decays are briefly reviewed; in particular those experimental programs designed to gain new insight on the Unitarity triangle and on the CKM mechanism by observing an hundred of events of the K + → π + ν ν ¯ decay are considered. This rare process, BR ∼ 10 −10 , is computed with very small theoretical errors, providing one of the cleanest tests of the Standard Model (SM) and, possibly, it could give some hints on the flavour structure of New Physics. A target accuracy of order 10% should be reached, thus making experiments in this field very challenging projects, expecially with respect to backgrounds suppression, particle identification capabilities and detector efficiency, while keeping costs and complexity at a reasonable level.

Study of gas Cherenkov detectors for high momentum charged particle identification

We present here an exhaustive study of the possibilities offered by a combination of a gas radiator of the highest index of refraction commercially available ( C 5 F 12 ) with the proven concept of large area CsI photocathodes instrumenting either a multiwire chamber or a GEM detector. We will present two geometries. One of them is proximity-focusing, nevertheless allows identification in a large momentum range. The second geometry deals with the possibilities of using focusing with a spherical mirror. Simulations of the performance are presented.

A 30 ps timing resolution for single photons with multi-pixel Burle MCP-PMT

We have achieved ∼30 ps single-photoelectron and ∼9.1 ps for multi-photoelectron timing resolution with a new 64-pixel Burle MCP-PMT with 10 μm microchannel holes. We have also demonstrated that this detector works in a magnetic field of 15 kG, and achieved a single-photoelectron timing resolution of better than 60 ps The study is relevant for a new focusing DIRC RICH detector for particle identification at future colliders such as the super B-factory or ILC, and for future TOF techniques. This study shows that a highly pixilated MCP-PMT can deliver excellent timing resolution.

The front-end electronics of the LHCb ring-imaging-Cherenkov system

The LHCb experiment at the CERN Large Hadron Collider will use ring-imaging Cherenkov detectors for particle identification. By measuring rings of Cherenkov photons generated by elementary particles traversing a radiative medium, these particles can be identified across a wide range of momenta. The photons will be measured by a new type of detector, the pixel hybrid photon detector (HPD). In total, 484 HPDs will be used, providing ∼500,000 channels of data. Specific readout electronics have been developed for processing the data from the HPDs, and this paper describes the design and testing of these devices together with the final system to be used in the experiment. Emphasis is on the application-specific integrated circuits that are encapsulated within the HPDs, allowing high channel density and low noise. These are subject to the strict requirements of efficient photon detection and reliability within the harsh environment of the experiment. Special interconnect techniques developed for this application are described. Finally, the additional electronics infrastructure to readout the full system of 500,000 channels is outlined, including data transmission and power distribution.

PAMELA SCIENCE

The PAMELA satellite-borne experiment1, to be launched in 2005, is a powerful spectrometer including a magnetic field tracker and particle identification detectors. PAMELA science is broad and includes studies of interstellar propagation, solar modulation and search for dark matter signals.

Development of photon detectors for a fast focusing DIRC

We report progress in developing a focusing DIRC with very good timing resolution. This basic detector development has been motivated by a possible upgrade of the very successful BaBar DIRC particle identification detector for a future Super B-factory. We have built a single bar full size prototype, which aims to reduce the chromatic error by precise timing, and to remove the effect of bar thickness with a focusing mirror. This paper describes the design of the prototype, and systematic studies of the timing resolution and position response for single photons for two 64-pixel detectors: (a) Hamamatsu Flat Panel PMTs, and (b) Burle MCP–PMTs. To test the prototype, we have developed new electronics for ∼300 pixels capable of measuring a single electron timing resolution to ∼100 ps. We also report on a first measurement of aging with the MCP–PMT.

Performance of the high momentum particle identification CsI-RICH for ALICE at CERN-LHC

The ALICE High Momentum Particle Identification (HMPID) detector consists of an array of seven identical proximity focusing Ring Imaging Cherenkov counters. It has been designed to identify charged pions and kaons in the range 1 < p t < 3 GeV / c and protons in the range 2 < p t < 5 GeV / c . The total active area of this detector is about 11 m 2 and represents the largest scale application of CsI photocathodes to date. The detector performance, as being evaluated in test beam at CERN, will be discussed for the first five modules.

Status of the HMPID CsI-RICH project for ALICE at the CERN/LHC

The ALICE (A Large Ion Collider Experiment) high momentum particle identification (HMPID) detector, presently under construction, consists of seven identical proximity focusing ring imaging Cherenkov (RICH) counters exploiting large area CsI photocathodes for Cherenkov light imaging. With a total area of 11 m/sup 2/, it represents the largest CsI-RICH system ever used in High Energy Physics. The detector layout, assembly and quality checks will be presented, with particular emphasis on CsI photocathodes mass production. A validation procedure has been established combining the results of the photocathode response mapping obtained in a dedicated VUV scanner with test beam data. The long-term stability has also been studied by irradiation with a Sr-90 source of a final size CsI photocathode inside a detector prototype.

Results from HARP

The HARP experiment at CERN is performing extensive measurements of hadron production cross sections and secondary particle yields in the energy range 1.5-15 GeV over the full solid angle, using a large set of cryogenic and solid targets. The hadron production in this region is a relevant ingredient in several branches of neutrino physics, including the characterization of neutrino beams, precise prediction of atmospheric neutrino fluxes, and quantification of pion production and capture for neutrino factory design. An overall precision of a few percent is required from the experiment to reach the final aim. The experimental layout comprises two spectrometers to perform momentum measurement of the secondaries produced in the target. The track momentum reconstruction in the spectrometers is complemented by a set of particle identification detectors that allow, with some redundancy, the particle type discrimination. Approximately 30 TB of data corresponding to 420 millions of events have been collected. The measurements of hadron production cross sections in the forward region (up to about 250 mrad) are reported using the K2K replica targets and a proton beam of 12.9 GeV/c. This is an appealing physics case given the immediate interest for those experiments and for the neutrino community.

The HERMES recoil detector: a combined silicon strip and scintillating fibre detector for tracking and particle identification

The study of hard exclusive processes at the HERMES experiment at DESY requires a recoil detector surrounding the internal gas target. It consists of a silicon strip detector inside the beam vaccum, a scintillating fibre tracker in a 1 T solenoidal field and a tungsten-scintillator sandwich detector for photon detection. This recoil detector will improve the selection of exclusive events by a direct measurement of the recoiling particle as well as by rejecting non-exclusive background events.

The HERMES recoil detector: a combined silicon strip and scintillating fibre detector for tracking and particle identification

The study of hard exclusive processes at the HERMES experiment at DESY requires a recoil detector surrounding the internal gas target. It consists of a silicon strip detector inside the beam vaccum, a scintillating fibre tracker in a 1 T solenoidal field and a tungsten-scintillator sandwich detector for photon detection. This recoil detector will improve the selection of exclusive events by a direct measurement of the recoiling particle as well as by rejecting non-exclusive background events.

Perspectives on the performance of a multilayer Silicon TRD (SiTRD)

The Silicon TRD (SiTRD) is a transition radiation detector consisting of multiple modules, each composed by a radiator followed by a silicon strip detector (SSD), inserted inside a magnetic field region. A full Monte-Carlo simulation of the SiTRD has been developed in order to study the performance of the detector for particle identification and momentum measurement. The simulation code, that describes the TR production and the processes of charges deposition and generation of electric signals inside the SSDs, has been tailored using the data taken with a 3– 5 GeV/c momentum electron–pion beam. The pion rejection power and the momentum resolution have been studied as a function of the detector parameters.

ϕ meson production in Au–Au collisions at GeV

ϕ mesons were reconstructed in the K+ K− channel in Au–Au collisions at GeV by the PHENIX experiment. ϕ invariant masses were reconstructed using a high resolution time-of-flight detector and electromagnetic calorimeters for particle identification, in conjunction with the excellent momentum resolution of the PHENIX tracking detectors. A description is given of the techniques for signal extraction and the corrections applied to obtain yields.

Charm identification using silicon detectors in a neutrino experiment

A target consisting of four passive layers of boron carbide and five layers of silicon microstrip detectors (NOMAD-STAR) with a total surface of 1.14 m2 was installed inside the NOMAD neutrino oscillation experiment at the CERN SPS. A sample of 45 charm mesons (with 22 background) was obtained from about 11 500 νμ charged current interaction in NOMAD-STAR. The efficiencies obtained from this search demonstrate the capabilities of silicon microstrip detectors for charm particle identification at a future neutrino factory.